Note: Descriptions are shown in the official language in which they were submitted.
w~ ~zi~oa~9 ~~ri~~~ l i~s~~=~z
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GOED CAR~BO?CYLATES AND PROCESS FOR PREPARING T~-iE
SAME
Technical Field of the Inven ion
The present invention relates to novel gold
carboxylates and methods for preparing gold carbaxylates.
Background of the Tnvention ..
Many types and mixtures of metal salts and soaps
of natural or synthetic organic acids, particularly carbox-
ylic acids, nave been suggested and commercially offered
over several decades. These have been used to supply
metals in forms which are soluble in organic liquids,.
particularly in various hydrocarban oils and solvents, to
form solutions having various desired ,properties and uses.
For example, such metal salts have found uses as catalysts
and as fuel and lubricant additives. Metal salts of
carboxylic acids also are useful as stabilizers for various
polymers including polyvinyl chloride~type plastics, and in
the area of drying catalysts for paints, varnishes and
other coating compositions.
However, since gold is 'che most noble of the
noble metals, gold is not dissolved by most acids under
ordinary conditions. Gold complexes, such as chloroauric
acid formed by the reaction of gold with aqua regia ( 3 a 1
hydrochloric:nitric acid), and alkali ~dicyano)gold(1)
formed by a reaction between gold and an alkaline cyanide
solution in the presence of air or hydrogen peroxide, are
compounds generally bound more strongly to 'the respewtive
anions than the ligands produced between gold and carboxyl-
ates, making it difficult to separate gall carboxyla~tes
from a solution containing 'these other ligancls a These
other ligands are considered axnelesirable :in a numbe:x o:f
applications in which gold carboxyla~tes would be desired.
w~ ~zi mass ~~ri us~~ ~ it~~-~~2
P'
274828
_2-
fox example, the catalytic and co-catalytio~
properties of gold may be inhibited by the presence off'
chloride ions or chlorine-containing compounds, such as
when gold is used as a catalyst for the production o~
phenol acetate. Nitrogen compounds such as amines, amides
and cyanides; phosphorus compounds such as phosphateq
phosphine complex compounds; and sulfur compounds such as
sulfates, sulfones, sulfoxides .and sulfides may also act as
a catalyst poison. The cyanides, of course, are also
undesirable from a human toxicological view~aoint.
U~S~ ~'atent 3,6E7,993 to Hornig, deceased, et al
describes a process for making solid gold hydroxy diacetate
of the formula Au (OH) (02CCH~) z and its use as a catalyst or
catalyst component for homogeneous or heterogeneous read
tions. It is also mentioned that the gold hydroxy diace-
fate may be used for manufacture of other organic gold
compounds such as reacting it with propionic acid, or with
other carboxylic acids, to yield a correspanding, gold
compound.
Takiguchi et al, °°Synthesis of naphthenates o:~
gold, silver, platinum and palladium and bisoxime palladium
dichlorides,°° ~agy~ I~agahu Zasshi, Vol. 72, No.7, (,Japan
1969) pp. 1549-1551, describes reactions of chloroauric
acid and chloroplatinic acid with sodium naphthenate, and
reports that the direct reaction between an agueous solu-~
Lion of chloroauric acid and sodium naphthenate lacked
reproducibility and yield and 'the direct reactions between
chloropla~tinic acid and sodium a~aphthenate caused marked
precipitation of metal and °°did not produce a good result.
°°
U.S. Patent 3,1o0,458 (Lindholm) describes a
chemical process for preparing noble metal salts og carbox-
ylic acids useful in photosensitive aa~d thermosensitive
compositions. The process involves mixing a non-aqueous
solution of an organic carboxylic acid with a non--aqueous
~'O 92/ 1 (9459 PST/ LJS')! /flt37{)2
solution of a noble anetal trifluoroacetate or tetrafluoro-
borate in the presence of an organic peptizer, A ~srariety
of organic peptizers are disclosed including polyvinyl
acetals and certain acryla~te copolymers.,
As far as the inventor is aware, none of °the
foregoing processes provides a facile means for obtaining
gold carboxylates, particularly gold carboxylates derived
from carboxylic acids having a molecular weight higher than
acetic acid. .
summary 2r the Invention
The present invention relates to gold carboxylate
products and a process for preparing gold salts of organic
carboxylic acids. The process comprises reacting an alkali
or alkaline earth metal salt of an organic carboxylic acid
with a gold salt in an organic liquid at a temperature
sufficient to form the desired organic gold carboxylate~
preferred organic liquids.are ones which are solvents for
the alkali or alkaline earth metal Garboxylate and the gold
salt, but which are not solvents for a salt formed between
the alkali or alkaline earth metal of the starting carbox-
ylate and the anion of the gold salt. The process of the
present invention results in the formation of the desired
gold carboxylates which generally are characterized as high
purity products. The products may be recovered as a -
filtrate and further purified by redissolving the product ,.
in a second organic liquid. The second organic liquid is
preferably different from the organic liquid used during
the above reaction procedure.
Solutions prepared from the gold carboxylates
have numerous uses. They are useful as homogeneous cata-
lysts and they may serve as starting materials for making
printed Circuits, electrical contacts, and hybrid intercon-
nects for electronic devices, electrodes, c~ecora~.ive
i~~ 92/10459 f~C r/~J~9i/4)~7t)2
f ,.,...
20~4~28
-~-
coatings on glass and ceramics, reflective coatings for
optical surfaces, pharmaceuticals, etc.
Description of the Preferred Embodiments
Gold carboxylates of the present invention may be
described by reference to the following formula:
O
Aux (R(C-O)y)~ (I)
wherein each R independently represents a hydrogen atom or
an organic group of valence y and x, y and z~each represent
a positive integer such that x = y z/3. The organic group
R may be any group containing predominantly carbon and
hydrogen atoms and may comprise one or more hetero atoms
such as nitrogen, oxygen, sulfur and/or halogen. Prefera-
bly, R comprises less than ten mole-percent hetero atoms.
More preferably, R does not contain any hetero atoms or
contains only oxygen atoms as hetero atoms. Examples of R
groups include aliphatic, alicyclic and aromatic mono-- and
polyvalent moieties. The aliphatic moieties contain from
1 to about 29 carbon atoms, the alicyclic moieties contain
from 4 to about 29 carbon atoms, and the aromatic moieties
contain fram 6 to about 29 carbon atoms, Generally, the
aliphatic moieties will generally cowtain at least about 3
carbon atoms, and will preferably contain at least about 5
carbon atoms, and more preferably at least about 7 carbon
atoms and will preferably contain up 'to about 17 carbon
atoms, more preferably up to about 11 carbon atoms and even
more preferably up to about 9 carbon atoms.
Examples of organic R groups include methyl,
ethyl, propyl, butyl, isobutyl, pentyl, isopewtyl, hexyl,
2-ethylbutyl, benzyl, nonyl, isononyl, decyl, neodcyl, .
dodecyl, palmityl, stearyl, oleyl, linolyl, etc.
In one embodimewt of the present invention, x
represents 1. Specific examples of such gold carboxylat es
~~~ 92/ 1 U~59 f'1't'/ L~S91 /x)87<)2
~~'~~d~8
..
include gold 2-ethylhexanoate, gold octanoate, gold iso-
octanoate, gold decanoate, gold neodecanoate, etc.
The process for preparing 'the gold carboxylates
in accordance with the present invention comprises, in one
embodiment, the steps of
(A) preparing a mixture of
(g) at least one alkali or alkaline earth metal
salt of an organic carboxylic acid, ..
(2) a°t least one gold salt hawing ,an anion other
than the carboxylate anion of (A)(1), and
(3) an organic liquid capable of at least partly
dissolving the at least one alkali or alkaline earth metal
salt of an organic carboxylic acid of (~,) and the a~t least
one gold salt of (2) , which is not a solvent for a salt
formed between the alkali or alkaline earth metal of (1)
and the anion of (2); and
(B) maintaining the mixture (A) at a temperature
below the decomposition temperas ure of componewts (~) (~,) ,
(~f.) (2) and (A) (3) and gold carboxylate product for a period
of tiane sufficient to form the gold carboxylate>
The gold salt may be selected from any which have ,.
an anion capable of forming an alkali or alkaline earth
metal salt of (~)(1) which is insoluble in the organic
liquid. Examples include gold chlorides, such as gold
trichloride and tetrachloroauric acid; nitrates; sulfates;
and bromides, such as gold tribromide>
As noted, the preparation of the gold carboxyl-
ates by the process of the present invention is conducted
in an organic liquid which can be any orga:raic liquid in
which the alkali or alkaline earth metal salts derived from
the alkali or alkaline earth metal carboxylate and the gold
salt are relatively insoluble. Examples of orclanic liqLaids
which can be utilized in the process of the present inven-
tion include carboxylic acids or anhydrides such as acetic
CA 02074828 2001-10-25
-6-
acid, propionic, butyr~i.c acid, 2-ethylhexanoic acid, decanoic
acid, isooctonoic acid, isononanoic acid, neodecanoic acid,
dodecanoic acid, etc.; esters and ester-acids of carboxylic
acids or anhydrides suc_:h as methyl acetate, ethyl acetate and
diethyl acetate; ketones such as acetone and methyl ethyl
ketone; hydroxy-containing organic compounds including
saturated aliphatic alcohols such as methanol, ethanol,
propanol, and butanol, unsaturated aliphatic alcohols such as
allyl alcohol, etc.; aromatic solvents including benzene,
toluene, xylene, cumene, psuedo cumene and mesitylene;
saturated ethers, e.g., saturated aliphatic ethers such as
di-n-propyl ether or di-isopropyl ether or a cyclic ether such
as tetrahydrofuran (THF') or dioxane; nitrile solvents such as
acetonitrile; halocarbons such as methylene chloride or
dichloroethane; etc.; or mixtures thereof. Among these, the
carboxylic acids or anYzydrides, ketones, saturated aliphatic
alcohols, aromatic solvents, saturated aliphatic ethers, and
cyclic ethers are preferred, and among these, acetone, methyl
ethyl ketone, propanol, xylene and THF are preferred.
The alkali or alkaline earth metal salts of organic
carboxylic acids from which the gold salts can be prepared
include salts of various single- and multivalent hydrocarbon
groups having one or mare carboxy group substituents such as
unsubstituted, substituted, or polyfunctional aliphatic,
alicyclic and aromatic mono- and polybasic carboxylates. The
organic carboxylates may be either natural or synthetic, or
mixtures thereof. Functional moieties include ether, ester,
thioester, ketone, amine, nitrile, and heterocyclic linking
groups and substituents. Examples of alkali or alkaline earth
metal salts of natural acids, although usually refined,
include alkali or alkaline earth metal salts of straight- and
branched-chain carboxylic acids, including mixtures such as
tall oil acids, and
w~ 92~a o~59 r~ rv use ~ inH~t~z
alkali or alkaline earth metal salts of cyclic carboxylic
acids such as naphthenates. ~ variety of synthetic carbox_
ylates, and particularly aliphatic carboxyla~tes or mixtures
thereof, are useful. The aliphatic ca~boxyiates used in
the present invention contain at least 1 carbon atom, and
generally at least 2 carbon atoms and may contain up 'to
about 30 carbon atoms or more. The alicyclic carboxyla~tes
can contain from 5 to about 30 carbon atoms. Aromatic
carboxylates contain from 7 to about 30 caxb~n atoms. The
alkali metal carboxylates are generally preferred :for the
low solubility of the alkali metal halides in many organic
liquids.
Generally, the aliphatic carboxylates will
contain at least ~1 carbon atoms, preferably contain at
least about 6 and more preferably at least about 8 carbon
atoms and in general up to about 18 carbon atoms, more
preferably up to about 12 carbon atoms and even more
preferably up to about ~.0 carbon atoms. Tn oaae embodiment,
at least about 80 weight-percent of the organic carboxylate
are these preferred aliphatic c%arboxylates. ~7hen metal
salts comprising more than one carboxylic acid are em-
ployed, the metal salts of carboxylic acids containing, for
example, at least about six carbon atoms raay be employed
advantageously in combination with metal salts of carboxyl-
ic acids having as few as two carbon atoms as one of the
acids of the metal salt mixture.
Examples of useful organic carboacyla~tes include
alkali and alkaline earth metal salts of acetic acid,
propionic acid, butyric acid, isopentanoic acid, hexanoic
acid, 2-ethyl butyric acid, benzoic acid, nonanoic acid,
decanoic acid, 2-ethyl hexanoic acid, isooctanoic acid,
isononanoic acid, neodecanoic acid, dodecanoic acid, lauric
acid, palmitic acid, stearic acid, olea.c acid, lir~oleic
acid, commercially available mixtures of 'two or more
CA 02074828 2001-10-25
_$_
carboxylic acids such as naphthenic acids, tall oil acids,
rosin acids, etc.
The alkali or alkaline earth metals of the carboxylate
reactants may be any which form a carboxylate which is soluble
in the organic liquid, but which form a relatively insoluble
precipitate with the anion of the gold salt reactant in the
same organic liquid. The expression "relatively insoluble
precipitate" is defined herein to mean that the alkali or
alkaline earth metal salt is sufficiently insoluble to drive
the reaction in favor of gold carboxylate formation. Generally
the organic liquid is selected such that the solubility of the
alkali or alkaline earth metal salt is not more than 1.0 gram
per 100 grams of the organic liquid. Preferably, the
solubility of the alkali or alkaline earth metal salt formed
during the reaction process is not more than about 0.001 gram
per 100 grams of organic liquid, and preferably the solubility
is not more than about 0.0001 gram per 100 grams of organic
liquid. Published solubility data, such as the solubility data
compiled in Linke, Solublities: Inorganic and Metallo-Organic
Compounds, 4th ed. (Amer. Chem. Soc'y. 1965) may be utilized
to select appropriate cation, anion and organic liquid
combinations. Examples include sodium and potassium
carboxylates combined with at least one gold halide in organic
liquids such as the acid corresponding to the carboxylate
moiety, another carboxylic acid, acetone, tetrahydrofuran,
etc.
The reaction between the starting gold salt and the
organic carboxylate can generally be carried out at
temperatures of from about 0°C to about 150°C for a period of
time sufficient to form the desired gold carboxylates as long
as condition (B) above is met. Generally, the reaction
CA 02074828 2002-O1-03
_g_
temperature rill be at least about 20°C, and often at
least about 45° and will generally be not mere than about
100°C, and often not more than about 80°C. A temperature
of about 56°C presently is preferred ,when the organic
liquid is acetone, since that is the reflux temperature of
acetone at atmospheric pressure. Generally, the reaction
will be completed within about 24 hours, and often will be
substantially complete within about 6 hours of when it is
initiated. Reaction times within about 4 hors can be used
to achieve a gold carboxylate product yield of at least 80
wt. ~ in most cases. Yields as high as 90 wt. ~ or higher
can often be achieved. The period of time required for
reacting the gold salt with any particular carboxylate ip
solution can be readily determined by one skilled in the
art.
After the reaction is completed, the organic
liquid generally is filtered to remove any undesirable
solids which may be present. The filtrate is a solution
containing the desired gold carboxylates. Depending on the
amount of organic liquid used in the reaction, ~ the filtrate
may be concentrated under vacuum to provide solutions
having higher concentrations of the gold carboxylate.
In another embodiment of the present invention,
the gold carboxylate is prepared by the above-described
steps (A), and (8), and optional steps of
(C) filtering the product of (B) and recovering
the filtrate and
(D) evaporating the organic liquid of (A)(3)
from the filtrate and redissolving the filtrate in a second
organic liquid different from the organic liquid of (A)(3).
In a preferred embodiment, steps (A) , (B) , (C)
and (D) are followed by the further steps of
(E) filtering the solvent containing the dis-
solved filtrate residue.
vd~ 92/ 1049 P~Cf / LJS~ 3 /t>f3792
20'~~~2~
_10_
Steps (C) and (D) , and optionally (:E) , further
refine the product obtained in steps (A) and ($) by utiliz-
ing an organic liquid which is a good solvent for the gold
carboxylate in step (D) relative to contaminants such as
the alkali and alkaline earth metal salts produced as a
byproduct. In one embodiment of the present invention, the
organic liquid of (A)(3) is a ketone and the second organic
liquid of (D) is an aromatic solvent. the ateps in one
preferred embodi~ient utilize acetone as the ~rgan3c liquid
in (A) (3) and xylene as the second organic l.~iqu.id in (i7) .
Contrary to the requirements of (A)(3), the
second organic liquids of (D) are not necessarily solvents
for the reactants of (A), namely the alkali, or alkaline
earth metal carboxylates and the starting gold salt, unless
it is desirable to provide conditions for continued reac-
tion between the reactants as in steps (A) and (~).
In yet another embodiment of the present invent
Lion an organic liquid may be used in the reaction step
that has a sufficiently high boiling point that i°t would be
difficult to remove the organic liquid from the gold
carboxylate by heating and reducing pressure wi'thou't
decomposing the gold carbaxylate. In that case, it may be
desirable to conduct -the reaction in a minimum amount of
the high boiling solvent and then rinse the reaction
vessel, precipitates, and filter medium with a volatile
gold carboxylate solvent into the filtrate solu-tion> ~aea't
and/or reduced pressure can rthen be rsed to remove 'the
volatile sol'rent without decomposing the gold carboxylate.
One example of such a protocol would be to conduct the
reaction in ~-ethylhexanoic acid and rinse the reaction
vessel, precipitates and filter medium w:i.th pewt~~ne,
collecting the wash, arid evaporating t:he pentane 'to concen-
trate the gold carboxylate in the .filtrate.
r
W~ 92/10459
~~~"/tJ~~mt»~t~z
~~'~~8~~
_Z1-
The amount of alkali or alkaline earth metal salt
of an organic carboxylic acid added to the mixture in step
(A) is not critical. Similarly, the concentration of the
starting gold salt in the mixture prepared in step (A) is
not critical and may be varied over a wide .range. General-
ly, the concentration of the starting gold salt will be
from about 1 to about 90% by weight, preferably from about ,
to about 20% by weight. Typically, 'the reactants are "
mixed in about stoichiometric amounts, but in. some instanc-
es an excess of a reactant may be used to force the reac-
tion 'to completion. Generally, the molar ratio of alkali
or alkaline earth metal carboxylate to starting gold salt
is in the range from about Z:l to about 10:1..
The amount of organic liquid added to the mixture
in step (A) should be an amouwt which will yield a solution
of the desired gold carboxylate in acceptable concentra-
tion. Generally, the solutions of the gold salts of
organic carboxylic acids obtained in accordance with the
present inventir~n preferably contain at least about 3 wt. %,
and more preferably at least about ~ wt.%, gold. The
concentration of PGM and/or rhenium can approach the
theoretical limit that may be present in the formulae for
the carboxylate salts sans solvent in which 'the number of
equivalents of PGM and/or rhenium equals the number of
equivalents of the carboxylate. Concentrations up to about
50% by weight or higher of gold can be obtained. Typical-
ly, the metal concentration is at least up to about ~0-s by
weight. The organic phase containing organic liquid and
the gold carboxylates can be further dilwted with solvemt
to provide solutions containing a desired concentration.
The organic solvent can be stripped from the gold carboxyl-
ate so that the gold carboxylate can be used neat or
redissolved in a completely da.fferent solvent, such as in
above-described optional step (D) , when 'the organic :lic~u.id
i~V~ 92/ 10459 f C ~~/ U:~9 7 /~7R'792
-la-
or solvent is sufficiently volatile. The solutions may be
filtered to remove suspended particles.
The following example illustrates the process of
the present invention and gold carboxylate solutions which
are prepared in accordance with the process of the inven-
tion. ~Jnless otherwise indicated in the following example
and elsewhere',in the specification and claims, all parts
and percentages are by weight, all temperatures are in
degrees Celsius, and all pressures are at ,or near atmo-
spheric.
Example 1
5.23 grams of gold trichloride, 9.05 grams of
sodium 2-ethylhexanoate and 12.1 grams of 2-ethylhexanoic
acid are mixed in a reaction flask. The mixture is warmed
to 50°C and stirred for 30 minutes. The slurry which forms
is then filtered and the reaction flask and filter funnel
are rinsed with pentane in portions which total about 50
mL. The filtrate is then warmed to 50°C under a mild
vacuum to evaporate the pentane. The product is a clear
yellow solution containing 3.27 grams of gold. 'Yield is
96~.
The stability of the products prepared in accor-
dance wa.th this invewtion can be improved by incorporatincJ
various solubilizing and stabilizing agents such as, for
example, ammonia, amines, chelating agents, amounts of at
least one of the above-described organic carboxylic acids
in excess of the amount required for the gold carboxylate,
etc .
The gold salts of carboxylic acids prepared in
accordance with -the present invention can be recovered and
isolated as crystalline solids, waxy solids, or oils
depending on the specific carboxyla~te us-ed. The techniques
for recovering these products from the solutions of the
present invention are well known in the art, such as by
'eW~ 92/1~459 f~'f/1J5~)1/f)87tJ2
'~'~~~' ~~~~~8~8
-13-
precipitation, evaporation, etc. Gold carboxylates can be
thermally decomposed at temperatures of about 250°C or
lower to form gold, and often at temperatures of about .
170°C or less. Such low decomposition temperatures are
advantageous for applying gold to temperature~sensitive
materials such as plastic and other organic polymeric
materials. This ability is particularly desired in the
electronics industry.
The gold carboxylates and gold carboxylate solu-
tions prepared in accordance with the present invention
also are characterized as being substantially free of
sulfur atoms and chloride, nitrate and other anions when
such atoms are avoided as hetero atoms in the above-de-
scribed R group. The absence of sulfur prevents the
emission of the objectionable noxious odors generally
associated with the decomposition of commerically available
gold-containing materials, particularly in connection with
decorative and electronic applications. The gold carboxyl-
ate products of the present invention generally have about
0.1 weight-percent or less sulfur present, and typically
contain 10 ppm or less sulfur when utilized in such appli-
cations.
The ability to form high concentration organic
gold solutions also has an advantage over certain pastes
now used which contain finely divided gold particles in
that a uniform thin coating of gold may be applied. This
advantage is particlarly valuable in 'the electronics field
and in the application of gold coatings on cJlass, ceramics,
and plastic.
As mentioned above, the gold carboxylates of the
present invention can be produced substantially free o.~
undesired cations such as chloride, nitrate and other
anions. An added benefit of the absence of such anions can
be the avoidance of undesired generatian of cart os.ive
VN~ 92/10459 t'~.°~'/LJ5f~1/t3~3'~{~Z
20"~ 4~2g
compounds generated during or after decomposition of
metallo-organo films produced from 'the carboxylates of the
present invention. Examples of such corrosive compounds
include hydrogen chloride gas, hydrochloric acid, nitrous
oxides and nitric acid. The benefit of avoiding such
corrosive compounds may be most noticeable when the
metallo-organo films made from the carboxylates of the
present invention are used in proximity to sensitive
components such as electronic components and acid-sensitive
substrates.
While the invention has been explained in rela-
tion to its preferred embodiments, it is to be understood
that various modifications thereof will become apparent to
those skilled in the art upon reading the specification.
Therefore, it is 'to be understood that the :invention
disclosed herein is intended to cover such modifications as
fall within the scope of 'the appended claims.
